“By themselves the volcanoes wouldn't be likely to cause the entire ice sheet to melt,” said lead researcher Max Van Wyk de Vries, whose team published the study in the Geological Society in late May. But if the glacier is already melting because of global warming, he said, “if we start reducing significant quantities of ice … you can more or less say that it triggers an eruption.”

In a worst-case scenario, the researchers say, we could see a feedback loop of melting ice that destabilizes volcanoes, which erupt and melt more ice, and so on until Antarctica's troubles to date seem halcyon in comparison.

“It could be bad news,” de Vries said. “But in a way it's good. The volcanoes would still have been there. Now we know the volcanoes are there.”

That we know at all is thanks in part to a chance discovery by an undergraduate student: de Vries, who at age 20 is still a year away from attaining his geology degree from the Scottish university.

For a class in his freshman year, he was looking through public data collected over several decades, which revealed what little is known about the landscape beneath kilometers of ice that cover much of western Antarctica. “I started discovering these cones,” he said.

De Vries grew up in a part of France dotted with volcanoes, so the shape was familiar. “I realized that maybe there was something special going on,” he said.

“Student's idea leads to Antarctic volcano discovery,” as the University of Edinburgh put it in Monday's announcement.

“We were amazed,” Bingham told the Guardian. “We had not expected to find anything like that number. … I think it is very likely this region will turn out to be the densest region of volcanoes in the world.”

A few dozen Antarctic volcanoes had already been discovered by explorers, such as Mount Erebus, which holds a lake of glowing lava on an island off the coast. But looking through decades' worth of data from ice-penetrating radar, seismic studies and other modern methods of exploration, the Edinburgh team gleaned the shapes of nearly 200 cones.

Some of these they ruled out from their study, because satellite photos showed no corresponding deformation on the ice above the cones. Another 50 or so cones poked above the surface of the ice and exactly matched the locations of previously discovered volcanoes. The other 91 cones, the team concluded, were true volcanoes that had never seen the light of day.

“Underneath an ice sheet is an environment you wouldn't usually expect a cone to be,” de Vries said. “They tend to erode into ridges or valleys.”

If the ice were to suddenly vanish, these volcanoes would poke out of the sea. Some would soar nearly four kilometers high. Volcanoes would cover Marie Byrd Land and skirt the Ross Ice Shelf, resembling dense volcanic clusters in East Africa.

And “there's the potential there are more volcanoes we haven't found,” de Vries said. “That's almost certainly the case.”

All the hidden volcanoes are relatively young, de Vries said — born beneath the ice no more than a few million years ago, when they first spewed lava into frigid waters. Whether they're going to do so again, co-researcher Bingham told the Guardian, “is something we will have to watch closely.”

Dying glaciers and volcanoes have been known to spar before. When Iceland thawed out 10,000 years ago, the land beneath the vanished ice rose up, and pressure-sensitive volcanoes spewed to life. In an age of rising temperatures, could Antarctica go the same way?

De Vries isn't sure. For all the stories about Delaware-size icebergs breaking off the continent, he said, “Antarctica as a whole has generally been doing better than most glaciers around the world. It's not melting rapidly like glaciers in the Rockies or Alps.” Still, he warned, “it is obviously a region that has the potential to be unstable. Some studies are finding it's started to melt, and we can't stop it.”

So, next question: If melting ice triggers one of these 91 buried volcanoes, or the 47 we can see, or who knows how many that have yet to be discovered elsewhere on the continent, what then?

While some are quite worried, de Vries doubted that a little blast of molten rock would do much harm to a massive Antarctic ice sheet. Directly, at least.

But he laid out a worst-case scenario in which lava managed to melt through a glacier, and warm ocean water seeped into the hole, and the whole system began melting even faster, potentially unleashing vast magmatic forces beneath the ice.

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